diff --git a/src/cli/config-manager/config-context.ts b/src/cli/config-manager/config-context.ts
index 78eb88d77..d01e8ba85 100644
--- a/src/cli/config-manager/config-context.ts
+++ b/src/cli/config-manager/config-context.ts
@@ -1,8 +1,13 @@
+import { basename, extname, join } from "node:path"
+
 import { getOpenCodeConfigPaths } from "../../shared"
+import { detectPluginConfigFile } from "../../shared/jsonc-parser"
+import { migrateLegacyConfigFile } from "../../shared/migrate-legacy-config-file"
 import type {
   OpenCodeBinaryType,
   OpenCodeConfigPaths,
 } from "../../shared/opencode-config-dir-types"
+import { CONFIG_BASENAME, LEGACY_CONFIG_BASENAME } from "../../shared/plugin-identity"
 
 export interface ConfigContext {
   binary: OpenCodeBinaryType
@@ -42,5 +47,20 @@ export function getConfigJsonc(): string {
 }
 
 export function getOmoConfigPath(): string {
-  return getConfigContext().paths.omoConfig
+  const configDir = getConfigContext().paths.configDir
+  const detectedConfig = detectPluginConfigFile(configDir)
+
+  if (
+    detectedConfig.format !== "none"
+    && basename(detectedConfig.path).startsWith(LEGACY_CONFIG_BASENAME)
+  ) {
+    const canonicalPath = join(
+      configDir,
+      `${CONFIG_BASENAME}${extname(detectedConfig.path)}`,
+    )
+    const migrated = migrateLegacyConfigFile(detectedConfig.path)
+    return migrated ? canonicalPath : detectedConfig.path
+  }
+
+  return detectedConfig.path
 }
diff --git a/src/cli/config-manager/write-omo-config.test.ts b/src/cli/config-manager/write-omo-config.test.ts
index 5701b53dc..83b70e9d3 100644
--- a/src/cli/config-manager/write-omo-config.test.ts
+++ b/src/cli/config-manager/write-omo-config.test.ts
@@ -1,5 +1,5 @@
 import { afterEach, beforeEach, describe, expect, it } from "bun:test"
-import { mkdirSync, readFileSync, rmSync, writeFileSync } from "node:fs"
+import { existsSync, mkdirSync, readFileSync, rmSync, writeFileSync } from "node:fs"
 import { tmpdir } from "node:os"
 import { join } from "node:path"
 
@@ -34,7 +34,7 @@ describe("writeOmoConfig", () => {
 
   beforeEach(() => {
     testConfigDir = join(tmpdir(), `omo-write-config-${Date.now()}-${Math.random().toString(36).slice(2)}`)
-    testConfigPath = join(testConfigDir, "oh-my-opencode.json")
+    testConfigPath = join(testConfigDir, "oh-my-openagent.json")
 
     mkdirSync(testConfigDir, { recursive: true })
     process.env.OPENCODE_CONFIG_DIR = testConfigDir
@@ -77,4 +77,41 @@ describe("writeOmoConfig", () => {
       expect(savedConfig).toHaveProperty(defaultKey)
     }
   })
+
+  it("migrates legacy oh-my-opencode.json to canonical oh-my-openagent.json before merging", () => {
+    // given
+    const legacyConfigPath = join(testConfigDir, "oh-my-opencode.json")
+    const canonicalConfigPath = join(testConfigDir, "oh-my-openagent.json")
+    const legacyBackupPath = `${legacyConfigPath}.bak`
+    writeFileSync(
+      legacyConfigPath,
+      JSON.stringify(
+        {
+          agents: {
+            sisyphus: {
+              model: "custom/provider-model",
+            },
+          },
+        },
+        null,
+        2,
+      ) + "\n",
+      "utf-8",
+    )
+
+    // when
+    const result = writeOmoConfig(installConfig)
+
+    // then
+    expect(result.success).toBe(true)
+    expect(result.configPath).toEndWith("oh-my-openagent.json")
+    expect(existsSync(legacyConfigPath)).toBe(false)
+    expect(existsSync(legacyBackupPath)).toBe(true)
+    expect(existsSync(canonicalConfigPath)).toBe(true)
+
+    const savedConfig = parseJsonc<Record<string, unknown>>(readFileSync(canonicalConfigPath, "utf-8"))
+    const savedAgents = getRecord(savedConfig.agents)
+    const savedSisyphus = getRecord(savedAgents.sisyphus)
+    expect(savedSisyphus.model).toBe("custom/provider-model")
+  })
 })
diff --git a/src/shared/opencode-config-dir.test.ts b/src/shared/opencode-config-dir.test.ts
index 5d6cf3ef5..7ddf8e009 100644
--- a/src/shared/opencode-config-dir.test.ts
+++ b/src/shared/opencode-config-dir.test.ts
@@ -289,7 +289,7 @@ describe("opencode-config-dir", () => {
       expect(paths.configJson).toBe(join(expectedDir, "opencode.json"))
       expect(paths.configJsonc).toBe(join(expectedDir, "opencode.jsonc"))
       expect(paths.packageJson).toBe(join(expectedDir, "package.json"))
-      expect(paths.omoConfig).toBe(join(expectedDir, "oh-my-opencode.json"))
+      expect(paths.omoConfig).toBe(join(expectedDir, "oh-my-openagent.json"))
     })
 
     test("returns all config paths for desktop binary", () => {
@@ -305,7 +305,7 @@ describe("opencode-config-dir", () => {
       expect(paths.configJson).toBe(join(expectedDir, "opencode.json"))
       expect(paths.configJsonc).toBe(join(expectedDir, "opencode.jsonc"))
       expect(paths.packageJson).toBe(join(expectedDir, "package.json"))
-      expect(paths.omoConfig).toBe(join(expectedDir, "oh-my-opencode.json"))
+      expect(paths.omoConfig).toBe(join(expectedDir, "oh-my-openagent.json"))
     })
   })
 
diff --git a/src/shared/opencode-config-dir.ts b/src/shared/opencode-config-dir.ts
index e1dedc401..7e07d4bb9 100644
--- a/src/shared/opencode-config-dir.ts
+++ b/src/shared/opencode-config-dir.ts
@@ -7,6 +7,7 @@ import type {
   OpenCodeConfigDirOptions,
   OpenCodeConfigPaths,
 } from "./opencode-config-dir-types"
+import { CONFIG_BASENAME } from "./plugin-identity"
 
 export type {
   OpenCodeBinaryType,
@@ -97,7 +98,7 @@ export function getOpenCodeConfigPaths(options: OpenCodeConfigDirOptions): OpenC
     configJson: join(configDir, "opencode.json"),
     configJsonc: join(configDir, "opencode.jsonc"),
     packageJson: join(configDir, "package.json"),
-    omoConfig: join(configDir, "oh-my-opencode.json"),
+    omoConfig: join(configDir, `${CONFIG_BASENAME}.json`),
   }
 }